1. Field of the Invention
The present invention relates to a centrifuge rotor having a plurality of liquid-capturing holes therein, the holes being arranged to capture a predetermined volume of liquid that may be liberated in the event of a container rupture.
2. Description of the Prior Art
A centrifuge rotor is a relatively massive member used within a centrifuge instrument to expose a liquid sample to a centrifugal force field. The rotor is provided with a plurality of cavities. The cavities may incline at a predetermined angle with respect to the rotor's axis of rotation, or may be oriented so that the axis of the cavity lies parallel to the axis of rotation. In the usual instance a container carrying a liquid sample is received within each of the cavities.
The container is subject to the risk of rupture during operation. In this event, depending upon the degree of inclination and the shape of the cavity, some or all of the, liquid sample carried by that container may escape from the cavity. If left unrestrained the liberated liquid may challenge the seal defined between the rotor and its associated lid, possibly exiting the rotor and entering the chamber of the centrifuge instrument. If the liquid is a biologically hazardous material its exit from the rotor is an especially catastrophic event.
Some prior art rotors attempt to forestall the exit of any liberated liquid from the interior of the rotor by disposing an annular lip about the periphery of the rotor body. The lip extends radially inward from the rim of the rotor and cooperates with the rim and the upper surface of the rotor body adjacent thereto to define an annular containment annulus. The containment annulus is sized to exhibit a containment capacity sufficient to hold an anticipated volume of liquid that may escape from a tube cavity in the event of rupture of one or more of the sample containers. Exemplary of rotors with a containment annulus defined by a containment lip are the rotors shown in Hereaus Christ catalog HC-E 11/1 dated April 1979. U.S. Pat. No. 4,372,483 (Wright) also illustrates a rotor with a containment lip. U.S. Pat. No. 5,071,402 (Weyant) shows a rotor having a containment lip and an arrangement of grooves disposed in surrounding relationship about the rotor cavities, with a bore being disposed in fluid communication with the grooves to expand the capacity thereof.
In the usual instance the provision of a suitably sized containment lip with a predetermined volumetric capacity is a sufficient response to the problem of liberated liquid. However, when a rotor is to be operated in a nonevacuated centrifuge instrument chamber (i.e., a chamber that contains some level of air pressure) a special problem with regard to containment of escaped liquid is presented. For such a rotor the direct expedient of providing a sufficiently sized containment annulus may not be available due to countervailing considerations regarding rotor windage.
Windage is the resistance, or friction, presented to a body as it is rotated or otherwise moved through air. In the context of a centrifuge instrument having a nonevacuated chamber, rotor windage is dependent upon the physical dimensions such as the diameter and/or height of the rotor as well as the size of the rotor with respect to the chamber in which it is disposed. Proximity of the rotor to the wall of the rotor chamber generates turbulent airflow that further increases air friction. Windage reduces rotor speed and, concomitantly, its performance for a given motor torque. Accordingly, it is not always possible merely to provide a containment annulus with a volumetric capacity sufficient to capture all the liquid expected to escape in the event of rupture of one or more of the containers in the rotor, as to do so may lead to a rotor that has physical dimensions (e.g., diameter and/or height) that would generate windage at a level sufficient to reduce the rotor speed and performance to an unacceptable level.
In view of the foregoing it is believed to be advantageous to provide a centrifuge rotor for use in a nonevacuated chamber that has a liquid containment capacity sufficient to capture and contain all of the liquid liberated within the rotor in the event of the rupture of one or more container(s), yet to do so in a way that maintains rotor performance, and reduces windage.